"About five minutes after the firemen left, I felt the vibration of a train moving down the track. I then saw the train move by without its lights on," he told Reuters.

"I found it strange its lights weren't on and thought it was an electrical problem on board.

"It wasn't long after that I heard the explosion. I could see the light from the fires in Lac-Megantic."

The spectacular crash saw flames shoot into the sky and burn into the night, levelling whole blocks in the centre of the town and destroying at least 30 buildings.

Environmental officials have warned that 100,000 litres of oil spilled in the disaster is headed for the Saint Lawrence river.

The centre of Lac-Megantic, a lakeside town of 6,000 near the border with Maine, remains cordoned off.

Police say they have been unable to examine much of the town because the area was still too dangerous.

Dozens of rail tanker wagons, some of them destroyed, are sprawled around the accident site.

Canadian crash investigators say they will look at the two sets of brakes on the train, the airbrakes and the handbrakes, as they probe what could turn out to be Canada's deadliest rail accident since 1956.